The present invention is particularly adapted for use with a nickel-chromium-iron alloy such as that described in copending application Ser. No. 917,832, filed June 22, 1978, now U.S. Pat. No. 4,236,943 issued on Dec. 2, 1980, which has strong mechanical properties and, at the same time, has swelling resistance under the influence of irradiation and low neutron absorbence. As such, it is particularly adapted for use as a ducting and cladding alloy for fast breeder reactors.
A material of this type is a gamma-prime strengthened superalloy; and its properties can be altered drastically by varying the thermomechanical treatment to which it is subjected. For nuclear reactor applications it is, of course, desirable to subject the alloy to a thermomechanical treatment which will produce the greatest irradiation-induced swelling resistance and/or the highest strength and most importantly the highest post irradiation ductility.